Police are thanking a group of Walmart heroes who suspected something suspicious when an elderly woman attempted to buy thousands of dollars of gift cards. (SBG)

LAS VEGAS (KSNV News3LV) —

Police are thanking a group of Walmart heroes who suspected something suspicious when an elderly woman attempted to buy thousands of dollars of gift cards.

Police say their investigation began with a call from two Port Linn, Ore., Walmart employees who refused to sell gift cards to a 90-year-old woman.

"She had bought, was trying to buy gift cards for an unusual amount, $3,000, which isn't something they see every day," Officer Jeff Halverson said to our Sinclair sister station in Portland, Ore.

At first, the woman couldn't explain why she was buying the cards.

“Finally got from out of the woman that the gift cards were for a gentleman representing himself as an IRS agent,” Halverson said. “He had convinced this woman that she had owed the IRS money and the only way that she could pay for it was to very secretively go down to Walmart and buy some gift cards and that he would then use the numbers to transfer that money into his account."

The officer drove the woman home as another called the scammer.

"Initially he tried to explain to him that he was the woman's son," Halverson said. “And when our officers identified themselves, he hung up the phone. And they weren't able to get in touch with him again."

No arrests were made which, unfortunately, is common in cases like this.

"I know I spoke with one a month ago, and then they ended up being out of a call center somewhere overseas," said Halverson. "It's almost impossible to track these guys down."

Police gave the Walmart workers a Challenge Coin, honoring them for doing the right thing.

"It would've been real easy for them just to sell it and walk away and go about their business," Halverson said. "But in their gut, they knew something was wrong."

Oregon authorities say the crime attempted at the store is the most common scam in the state.

They add that if you ever do get a call from someone claiming to be with the IRS or threatening arrest — and your ticket to freedom is a gift card — stop right there. That's a clear sign of a scam.